1. Field
The exemplary embodiments generally relate to motors for use in vacuum or corrosive environments, for example, in substrate processing apparatus.
2. Brief Description of Related Developments
Generally, motors used in applications such as semiconductor fabrication are typically configured as brushless DC motors. A rotor for these applications may generally include a number of permanent magnets incorporating rare earth materials. Special fixtures may be required to bond the permanent magnets to the rotor. Existing direct drive technology, which for example uses permanent magnet motors for actuation and optical encoders for position sensing, exhibits considerable limitations when, for example, the magnets, bonded components, seals and corrosive materials of the direct drive are exposed to ultra-high vacuum and/or aggressive and corrosive environments. In order to survive corrosive or high vacuum environments, the permanent magnets are generally required to be encapsulated and sealed in order to avoid magnet degradation.
Stators for these applications are usually constructed of laminated ferromagnetic material with complex slot shapes, multiple phases, and overlapping coils. Construction of a conventional laminated stator requires several complex manufacturing steps in order to assure proper assembly, lamination bonding, coil winding and installation and proper machining to meet tight tolerances.
It would be advantageous to provide a rotor that is vacuum compatible, corrosion resistant, non-laminated, and that does not utilize rare earth materials. It would also be advantageous to use a non-laminated stator with a simplified construction. It would further be advantageous to provide a motor with a shorter flux path that results in lower eddy current and iron losses, and provides a higher torque capacity.